1. Field of the Invention
This invention generally relates to a prosthetic apparatus for augmenting a musculoskeletal structure for maintaining or improving said structure, and more particularly to a prosthetic implant for use in reconstructed or replacement knees or other joints.
2. Related Art
Different apparatus have been developed to enable a surgeon to replace damaged osseous and/or articular material of the muscoskeletal structure with prosthetic devices or structures in order to preserve or restore the structural or kinematic function of the body. Keeping in mind that the ultimate goal of any surgical procedure is to restore the body to normal function, it is critical that the quality and orientation of any bone cuts, as well as the quality of fixation, and the location and orientation of objects or devices attached to the bone, is sufficient to ensure proper healing of the body, as well as appropriate mechanical function of the musculoskeletal structure.
While the implant of the present invention has applications throughout the human body, the applications and embodiments shown and described herein are specifically configured for total knee replacement, a surgical procedure where planar or curvilinear surfaces are created in or on bone to allow for the proper attachment or implantation of prosthetic devices. It should be noted that the apparatus and methods set forth herein can modified and applied to any form of joint replacement wherein the function to be restored is dictated by both static and dynamic principles, as well as forms of muscoskeletal reconstruction which are dictated primarily by static principles of operation.
Currently, bony surfaces to be resected or cut are done so in a series of planar surfaces. In total knee replacement, a series of curvilinear surfaces or resections are created in the bone to allow the attachment of a number of prosthetic devices to the femur, tibia, and patella. In the case of the femur, the posterior and distal femoral condyles, the anterior femoral cortex, and other anatomic features are referenced to determine the location and orientation of the resections. The location and orientation of these resections are critical in that they dictate the quality of fixation of the prosthesis to the bone, as well as the final location and orientation of the prosthesis.
There are several major problems inherent in current implant designs caused directly by the need for interior and predominantly planar fixation surfaces (these surfaces are interior surfaces of the implant which mate with the resected bone) embodied in implant designs whose external geometry is predominantly curvilinear. These problems include:
a. the removal of excessive amounts of viable osseous tissues; PA1 b. non-optimal or "unnatural" patellofemoral kinematics; PA1 c. excessive implant rigidity resulting in stress shielding of living bone; PA1 d. stress risers at the vertices of the planar fixation surfaces of the implant leading to potential failure sites under fatigue loading, and PA1 e. excessively massive implants resulting in additional material costs.
Past efforts have not been successful in properly addressing these concerns. Such previous efforts at implants are set forth in the following patents, none of which teach or suggest all of the benefits and advantages of the present invention. These previous patents include:
Goodfellow, et al., U.S. Pat. No. 5,314,482, discloses a femoral implant having a convexly shaped spherical articulation surface and a securement surface having major and minor areas at opposite end portions. The major area is essentially concavely spherically concentric with the articular surface to form a shell body part. The minor area is essentially planar and extends chordally of the articulation surface. The implant further includes a bone-penetrating pin extending radially from the major area in a direction parallel to the longitudinal direction of the minor area.
Walker, et al. U.S. Pat. No. 4,822,365, discloses a method of designing a prosthesis having convex male and concave female portions. The surface of the condylar male portion of the prosthesis is generated by analysis of either an average or specific condyle, or a distortion thereof to fit observed general dimensions of a specific patient. The female surface includes flexion and laxity surfaces. The flexion surfaces are generated by plotting the path of articulation of substantial points of contact between the male portion and a corresponding female portion. The laxity surfaces comprise raised guide-bearing surfaces for resisting dislocation of the condylar portion.
Hanslik, et al., U.S. Pat. No. 4,770,663, discloses a knee joint endoprosthesis comprising a femur with two skid surfaces and a space therebetween. The skid surfaces are interconnected at a front end. The skids having a curvature increasing from the front end to a rear end. The skids are also curved on planes perpendicular to the curvature. The joint endoprosthesis further comprises a tibia component having two surfaces on which the skids ride.
Zichner, et al., U.S. Pat. No. 4,662,889, discloses aknee joint prosthesis having a C-shaped femur cap for attachment to a resected femur condyle. The cap includes an aperture therethrough for receiving a shaft. A cap is also placed over the tibia. A connecting member is implanted into the tibia and interconnected with the femur by the shaft.
Shoji, et al., U.S. Pat. No. 4,586,933, discloses a knee implant having a femoral component with a curved articulating surface, movable inserts positioned between the femoral component and a tibial tray, the inserts having concave articulating surfaces at the top and bottom thereof, and a tibial tray with convex tracks and posterior stops.
Johnson, et al., U.S. Pat. No. 4,568,348, discloses a knee prosthesis having a femoral component for attachment to the femur, a tibial component for attachment to the tibia and a meniscal component positioned therebetween. The tibial component has a concave bearing surface. The meniscal component has bearing surfaces complimentary to the tibial component and the femoral component. The femoral component has a two-part curved bearing surface including a first curved portion and a second curved posterior portion contiguous with and of relatively lesser curvature than the first curved portion.
Schurman, et al., U.S. Pat. No. 4,358,859, discloses a knee prosthesis comprising a femoral implant having a condyle section and a stem, and a tibial implant having a tibial plateau and a stop plate and a stem.
Forte, et al., U.S. Pat. No. 4,353,135, discloses a knee implant having a patellar flange comprising a curved base and a pair of condylar runners.
Russell, et al., U.S. Pat. No. 4,722,330, discloses a distal femoral surface guide for mounting on an intramedullary alignment guide for use in shaping the distal femoral surface. A conventional shaping means such as an oscillating saw or hand saw is introduced into slots in the surface guide to resect the femur. The device also includes stabilizing members that extend along the sides of the femur to stabilize the device. The attachment surface of the implant comprises a series of planar surfaces.
Lackey, U.S. Pat. No. 5,053,037, discloses a femoral drill guide with interchangeable femoral collets, a femoral reamer and a femoral anterior/posterior cutting block with an adoptable anterior femoral ledge. A plurality of diagonal slots are provided for making diagonal cuts in the distal end of the femur. The attachment surface of the implant comprises a series of planar surfaces.
Ferrante et al. U.S. Pat. No. 5,098,436, discloses a modular guide for shaping a femur comprising a first bracket defining a generally U-shaped structure having an internal surface adapted to be seated on the distal aspect of a resected femur bone and an elongated central opening appointed to expose a selected area of the resected femur, including a curved track for guiding a first shaping tool along a predetermined path for controlled shaping of a curved patellar groove and a portion of the selected area exposed through the opening. A second bracket defines a linear slotted bore extending generally parallel to the long axis of the femur for guiding a second shaping tool to form a relatively deep recess accommodating an intercondylar-stabilizing housing of a knee implant.
Poggie, et al., U.S. Pat. No. 5,250,050 discloses an apparatus for use in preparing the bone surfaces for a total knee prothesis, comprising cutting guides, templates, alignment guides, a distractor and clamping instruments. The instrument for alignment of the cutting surface for resecting the tibia includes an ankle clamp, an adjustable alignment rod, and a cutting platform. After the cutting platform is properly aligned on the tibia, it is pinned thereto and the tibia may be resected using an oscillating saw. Also disclosed is a patella resection guide comprising a scissor-type clamp having distal gripping arms, each of which define a cutting surface, and gripping teeth. The attachment surface of the implant comprises a series of planar surfaces. Caspari, et al., U.S. Pat. Nos. 5,263,498, 5,228,459, and 5,304,181 disclose a method and apparatus for orthoscopically preparing bone surfaces for a knee replacement. A tibial jig is attached to the tibia at just above the ankle at a lower end and to just below the tibial tubercle at an upper end. One portal is formed in the knee for insertion of an orthoscope for viewing the knee, and another portal is formed for introducing resecting instruments. A cutting platform is aligned and secured in position and a cutting module is attached. Initially, a plunge cut across the tibial eminence is produced. This procedure is repeated until the surface of the tibial plateau is covered with trails having ridges therebetween. Thereafter, the device is passed back and forth over the tibial plateau to remove the ridges. The attachment surface of the implant comprises a series of planar surfaces.
Whiteside, U.S. Pat. No. 4,474,177 describes instruments for creating the distal femoral surfaces where a guide is used to index a flat surface used to guide the distal femoral resection. The attachment surface of the implant comprises a series of planar surfaces.
Kaufman, et al. U.S. Pat. No. 4,721,104 describes a method of preparing the intracondylar area of the distal femur. The attachment surface of the implant comprises a series of planar surfaces.
Collomb, European Application No. 538153-A1, discloses a modular device for positioning a knee prosthesis on a bone. The attachment surface of the implant comprises a series of planar surfaces.
Bert, et al., U.S. Pat. No. 5,234,433, discloses a method and apparatus for unicompartmental total knee arthroplasty. The attachment surface of the implant comprises a series of planar surfaces.
Pynaov, Russian Application No. 577,020, discloses an instrument for shaping the end joint of a bone to prevent arthrosis and ankylosis. The instrument is used to remove a central portion of the joint so that the joint ends are contacted in one plane without causing irritation in the paraarticular tissues. No implant structure is disclosed.
None of these previous efforts, however, disclose all of the benefits and advantages of the present invention, nor do these previous patents teach or suggest all the elements of the present invention.